Uploaded JPGs get pixelated - Why?

illapino

New member
I use Adobe's Photoshop to render JPG files, and I always turn up the output quality to the highest it can go, but by uploading them to social networking websites, they become pixelated in some areas, especially i noticed in certain hues. The quality of an uploaded photo is nowhere as perfect as it was the way I rendered and saved it as. Why is this and how can I prevent it? I thought it would be because such sites re-encrypt all incoming JPGs, but I've seen plenty of other profiles' photos that don't have my problem at all. What other settings in Photoshop (ImageReady) should I apply when saving and rendering JPG files??
 
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_SG_

It's All In The Beat
The sites compress and **** it all up. Same reason when you upload tracks to your myspace player it sounds real ****ty.
 

illapino

New member
No. Like I said, I've seen other people who don't have pixelation problems after uploading. Facebook also doesn't have this problem.
 

trezza

New member
That's why I use Corel for that particular purpose. Corel's photopaint has a better jpg encoder with more knobs so you can get it down to smaller sizes with fewer artifacts. Adobe photoshop is fabulous for many things, but not encoding, IMO.

That said, when I upload my images online, I make much smaller images from the original before I upload to social networking sites.
I try to get < 100k. So take a look at what you are uploading. Is it small enough? You can also set the image size in photoshop to 72dpi which is better for the web as opposed to 300dpi which is printer quality.

Good Luck!
 

illapino

New member
72dpi instead of 300dpi? I thought a higher number means higher quality regardless of the image's dimensions ............
 

trezza

New member
Yes, you're right, but if the network site has a physical size limit or a dimensional size limit and you ignore it, they will use a brute force algorithm to reduce the bandwidth or size required to deliver your image. When you do it, you have control over the outcome and can achieve a better result.

Also, if you downsize an image and then scale it up, you will get pixelation. You want to try to avoid that as well.

Do you have a link to your image both the high res/pixelated versions?
 

illapino

New member
could please explain "downsize an image and then scale it up"?
At which points of this are you referring to image dimensions and image memory size ?
 

trezza

New member
Ok. Let's say you have a 4"x4" image at 300dpi. In pixels, that's 1200x1200 pixels. That will make a nice 4"x4" picture on paper, but you don't have to have it like that on the web where 72dpi is common. My monitor has a resolution of 1600x1200 over 16"x12" or 100dpi, and that's not typical. 72dpi is typical for the web. The 1200x1200 image would be too big on the screen and take up lots of bandwidth when you display it.

So you can safely shrink your image to 72dpi (or 100dpi if it makes you feel better) unless it is part of a press kit. And your 4"x4" image at 72dpi will still look as good on screen as the 300dpi version does on paper at the same physical size (4"x4").

*However*, if you try to display the 4"x4" 72dpi picture at a larger resolution (say, 6"x6"), then it will pixelate and won't look as good. Instead, understand the target display size and scale the image down from the highest resolution appropriately (300dpi in this case).

Another thing to look at is the compression and smoothing. Again, Corel is better at this, but if your image has a lot of the same color, then some compression (10-15%) will not really be noticable.

Don't try to compress really small images like thumbnails.

Does that make sense?
 

illapino

New member
What I failed to mention is that pixelation occurs in areas of an image where I personally paintbrushed them with my mouse. Everywhere else is usually fine and not pixelated. But places where I sprayed some 'paint' to edit an existing image: that's where pixelation is rampant after uploading ... Can you explain this phenomenon?
 

trezza

New member
There may be a mismatch in the grain and compression of those areas will be different. Zoom in close to unedited areas and compare to the edited areas. Do the grains match?
 

illapino

New member
The file I work with when spraypainting is completely smooth coz I make sure to edit with a paintbrush till my edit is completely unnoticable, but as soon as it's uploaded, the uploaded image pretty much tattle-tales on my edits and blurry pixelation is visible in those areas where I worked on! I then look back at the working file prior to rendering and prior to uploading: completely flawless!

Makes no sense!
 

harmonized1

New member
make sure you stay at 72 res and change your jpeg compression to baseline standard. Also make sure you flatten the image before you export final file to be uploaded. The paint thing may occur because the myspace compression reads your paint as 1 single color. there for tries to block it to smallest area compression.
 
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